Other ways of reducing is to be on the "yarn diet". Lots of my recent projects have been exclusively from my stash. Here's Elsebeth Lavold's Cable Cotton purchased September 3, 2009 in Albuquerque at Village Wool.
Girly Cardigan by Mission Falls
Most yarn I buy with a project in mind, and if it isn't started immediately, it often languishes in my stash until... an imminent project arises. See my CONTEST PIECES which are all from stashed yarn. And contest prizes will contain yarn! Win-Win!!
Ravelry Link: HERE to Celinas-Mor